


Fundamental Frequency (the Angel in the Back Seat remix)

by filenotch



Category: Supernatural
Genre: M/M, Memory Loss, POV Outsider, Remix Redux, Season/Series 04
Language: English
Status: Completed
Published: 2015-06-19
Updated: 2015-06-19
Packaged: 2018-04-05 04:13:31
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,738
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4165365
Author URL: https://archiveofourown.org/users/filenotch/pseuds/filenotch
Summary: <blockquote class="userstuff">
              <p>
  <i>The note changed, taking on a familiar overtone, and Castiel watched as Dean-now did what Dean-then knew best, shooting at the ghosts while running, and reloading by touch while instinct led him to dodge and leap and win. The overtone was one of violence, righteous, strung with a joy untempered by the sense of duty that had weighed Dean-then. Castiel followed them to the car, watched as Dean-now leaned his head out the window with a loud noise, giving shape in the air to that joy.</i>
</p>
            </blockquote>





	Fundamental Frequency (the Angel in the Back Seat remix)

**Author's Note:**

  * For [rivkat](https://archiveofourown.org/users/rivkat/gifts).
  * Inspired by [Only Sweeter](https://archiveofourown.org/works/3188) by [rivkat](https://archiveofourown.org/users/rivkat/pseuds/rivkat). 



Castiel paused, flexing all his senses. The thread—the harmonic vibration that was Dean Winchester—it had changed. Small changes happened always, the stochastic nature of being. Such changes would not call to his attention. But the thread—the harmonic that was Dean Winchester—rang almost beyond recognition, the waveforms collapsing from the complex, dark dissonances of _Dean_ into a single, clear note. 

Castiel manifested in the back seat of the Impala, invisible. It took him a microsecond to sort why it all seemed wrong on the surface, wrong beyond the fundamental note that had changed. They were backwards. Sam drove. Dean talked. 

"…n't believe no one knows anything about this! Demons. Faeries. Vampires, too, right?" 

Sam didn't take his eyes of the road. "Yeah." The calm tone was belied by Sam's emotion spiking wildly through his harmonics.

"How did I even know about it?"

Dean's question barely rippled his new, pure waveform.

"Most people wouldn't want to know," Sam said.

"I must have found out somehow. I could be a hunter. I was there. I had weapons."

Sam snorted and looked over. "I guess you weren't very good at it." Castiel could hear the snap in Sam's tone, and had he been fully in a human vessel, limited by the physicality, that would have been all he knew of Sam's meaning, and he would have argued for Dean's skills. Here with all of his attention, he could sense that Sam wanted to distract Dean from asking about hunting. Castiel looked back upon their timeline, and saw the Trickster god, faerie-formed, wipe all of Dean's memories, and back a moment more to know Sam had been given the choice of his memories or Dean's, and in a flash of inspired love, told the thing to take Dean's. Take the memories, take the pain.

And Dean, wiped clean, responded to Sam's snap with chagrin and only a little bit of defense. "Maybe I'm just new to this hunting business?"

"I guess so," Sam said, "and maybe if you don't know why you hunt, you could get out of the business." Castiel wondered why Sam would lie, and in that moment of wondering, knew the answer. "What _do_ you remember?" 

Castiel reached in to Dean, not enough to violate, but to feel the edges and the depths, and Dean had fewer boundaries, less … Less weight. His harmonic had changed, become less complex, because he remembered nothing, carried no burdens of obligation, of loss, of pain.

Dean looked out the window, eyes landing on the sign for a diner. "I like pancakes," he said in answer to Sam's question, and his tone carried a note of defiance, but Castiel felt Dean's tiny surge of joy at memory, clear, of forkfuls of fluffy pancakes, laden with sweet syrup, of knowing the syrup came from tree sap. He knew things, just not who he was. 

Castiel considered Sam for a moment. Sam would not tell Dean who Dean was, or even who Sam was. He had, given the choice, given up his brother. He believed the wipe of Dean's memories was a mercy. He no longer remembered Hell. He no longer knew that there were angels. Castiel touched insubstantial fingers to the back of Dean's head, removing from his body the one thing that might most easily take him back toward corruption and despair, even without his memories. All trace of craving for alcohol--the deep addiction that Dean had developed to dull the memory of Hell, of need--this Castiel removed. 

Michael's intended vessel was now pure. 

+++

The note changed, taking on a familiar overtone, and Castiel watched as Dean-now did what Dean-then knew best, shooting at the ghosts while running, and reloading by touch while instinct led him to dodge and leap and win. The overtone was one of violence, righteous, strung with a joy untempered by the sense of duty that had weighed Dean-then. Castiel followed them to the car, watched as Dean-now leaned his head out the window with a loud noise, giving shape in the air to that joy.

"Told you!" Dean said, pulling his head in. "I am an awesome badass."

Happiness came off of Dean in waves, palpable to Castiel in this state, but appearing to break around Sam, stiff in the driver's seat. Castiel could hear Sam trying to find the words that would make Dean leave the hunting life, to go and be happy and safe, but Castiel knew that Dean could do no such thing. 

The skill of the body would serve Michael well.

+++ 

A familiar-not-familiar sonority rang loud, then settled, recalling the righteous anger and duty, fierce love and pain of Dean-then. Dean-now's pain was sadness and something else. 

Castiel sent part of his awareness into a hotel room at the time of the note, to see what caused it. It looked like so many other such rooms stretching before and behind Sam and Dean-then-and-now, with the computers on the table, the weapons on a towel on one of the beds. 

"I'm sorry," Sam said, "but there's nothing matching your description in missing persons."

Castiel could feel the deep hollow open in Dean, but deep only in context of Dean-now, and only hollow, nothing like the pillar of rage and self-disgust, cased by duty, that had defined him in the months since he'd been pulled from Hell. Dean-then had looked at Sam, and felt, believed, he did not deserve his love, any love. Dean-now looked at Sam as a stranger kind enough to help someone without a memory, saw a man who had loved a brother. And Dean-now, with no one looking for him, knew that no one loved him. The unworthiness, though, was a more familiar tone than the sadness.

Castiel did not touch that pain, and let the hollow inside grow. The need would make Dean eager to be filled. The purpose that Michael would offer his vessel would serve for love and worth.

+++ 

Bright and clear, the added note rang high, and when Castiel sent his awareness to where Sam and Dean-now stood in yet another hotel room, he could not immediately see the reason for the change. It was a small thing, but a large thing, and Dean-now looked at Sam with anticipation, and Sam looked into a box that held a small piece of electronics. A gift, something Dean-then would never have done. "Means you can surf lots more places," Dean-now said, but Castiel did not understand the reference.

"Thanks," Sam said, and the emotions Castiel felt from him were both confused and happy. "It's perfect." 

At those words Dean-now's notes rang with joy, but Dean ducked his head to hide its expression from Sam. "Well, you know. Wouldn't want to get caught out on a hunt with no way to look stuff up." And Castiel felt something new in Dean-now, and the hollow at his center was a little less empty. 

+++ 

_*Castiel*._

The voice of command could not be ignored. Castiel pulled his awareness from watching Dean-now play chess. Dean-then had been a brilliant field tactician, best in response to a threat, but not one for long-term planning. Dean-now used strategy and tactics, both. _+Zachariah+_

_*You watch Michael's vessel.*_

Castiel could not read the tone of Zachariah's voice. _+Yes, as I have done from time to time since we raised him from Hell. He does not know who he is.+_

_*A curse. We know. We have others watching him. You did not report it.*_

Zachariah's words contained rebuke. Castiel said, _+I apologize. It did not seem necessary. In many ways he will be a more pure vessel.+_

Zachariah's mien seemed grim, and somehow, oddly, gleeful at the same time. _*You know the demons are trying, right now, to break the seals and free Lucifer.*_

The tone confused Castiel, which came out in a slight disrespect. _+You tell me nothing I do not know.+_

_*The first seal has been broken.*_ Castiel did not answer. The information also was not news. _*Do you know what the first seal was?*_

_+I do not. I know what work is assigned to me as a soldier of our garrison. I have not needed to seek further knowledge.+_

_*A righteous man stepped off the rack and picked up the tools of torture in hell.*_

Again, Castiel felt something in Zachariah's words that discomfited him. News that should have been grave he delivered casually, offhandedly. With nothing more from Zachariah, Castiel knew the name of the righteous man. After all, he had been surprised to find them rescuing one who held the knife. The new knowledge burned through Castiel. Dean-then. Dean-then had picked up Alistair's tools. The rescue was made only after, and there was no reason for that, except... _+Was this curse part of the Plan?+_

 _*If it happened, it must be*_ Zachariah answered, the offhandedness of his delivery making the words seem like a lie. _*But that plan is now in some disarray. For Dean Winchester would hardly have agreed to be Michael's vessel before experiencing Hell. Taking Michael was meant to give him a way to escape from his guilt, to atone, even. His experience of giving the pain in Hell would have prepared him for what Michael may need to do in righteousness to win the coming war.*_

 _+But if Lucifer takes Sam+_ Castiel said, _+would it not suit the Plan that Dean not know they are brothers, and thus not resist if Lucifer and Michael must fight?+_ As he said it. Castiel wondered about the word _if_. If breaking the first Seal was part of the Plan…

Zachariah said, _*That is, of course one possible silver lining.*_ His tone changed from speculation to commander. _*Report.*_

Castiel told Zachariah all he had observed, emphasizing that Dean-now felt an emptiness that Michael might fill.

 _*All to the good then. You see, it is Dean's destiny. Everything that happens to him will make him a fitting vessel.*_ Then Zachariah was gone.

Castiel thought back on the conversation. If breaking the first Seal was part of the Plan… He could not finish the thought. And Zachariah did not seem at all bothered by the breaking of the Seal, not gravely concerned that the Apocalypse was nigh, not at all concerned about how a small human mind would react to the memories of Hell. He had let Dean turn, let him remember, given pain on purpose. Castiel looked back on all of his interactions with Zachariah, reassessing.

Before he knew Dean Winchester, Castiel would not have had a word for how Zachariah had sounded and felt, not just now, but always. Now he had two words to describe his superior officer. Smarmy douche.

+++ 

He watched them, Sam and Dean, for moments here or there. Sometimes Dean, touching the cicatrix of an angelic hand print, would pull Castiel's attention, and little seemed to change. But change had happened, and he had missed it, a slow swell that Castiel only noticed when it reached the threshold of action. Dean-now was in love.

It was a motel room, and Dean straddled Sam's lap, kissing him, ringing notes of joy and want and fear and _love_ , not so deep as Dean-then had loved Sam, but pure, the threads of fear and duty no more than they should be for a comrade in arms. Castiel knew those feelings well, felt them for many of the soldiers in his garrison—fear for their safety, his own duty to protect them. Dean-now had this and more. There was admiration, gratitude, and a strange joy simply at the fact of Sam existing in the world.

The feeling threaded through the meshwork that had been slowly filling into the hollow places of Dean, a scaffold that might be filled in later. 

And then the kiss broke as Sam wrenched his head back, panting, full of desire and fear and remorse. Dean's hand dropped away from Sam's cheek as Sam said, "No." Castiel could hear the conflict in Sam's voice, but it let it be, let the scene play out. Sam would see this as a sin, even if Dean-now didn't. "There are—" Sam started. "We don't even know why this could be a bad idea."

"Sam," Dean said, "if you don't want this, stop talking about me and start talking about you."

Sam inhaled. "I don't want this." And Castiel knew the lie for what it was, respected that Sam would strive to do what he thought was right. Castiel was not sure Sam was right to hold back, and a Dean that was not empty would have a true choice of whether to say yes to Michael. 

+++ 

Moments, here and there, Castiel looked in on them. Dean-then... even Castiel knew that Dean-then was purposeful in irritating his brother. Dean-now took all that same attention, and turned it to pleasing. Sam basked in the attention more than Castiel thought he would ever admit, and he knew it was only a matter of time.

And when the note of completion resonated through Dean, Castiel manifested in their room. Sam was stretched out and glistening on the bed, his fingers threading through the short hair on Dean's head, where Dean gave Sam pleasure with his mouth, Dean's entire being welling up with joy and want fulfilled… He did not monitor the wavelengths of light, for what they did with their bodies interested Castiel not at all. Instead he felt the subtler harmonics, felt where Sam and Dean meshed in a new way, different from when Dean knew they were brothers-by-birth, from when Dean-then's love for Sam had mixed with obligation, old resentments, impurities.

And this was love. Other angels might find fault with the fornication, but Castiel could not. Sam had sacrificed Dean-then to save Dean, sacrificing at the same time his own need for a brother who knew him. He was gifted with Dean-now, whom he loved with a new love wrapped around the old. Dean was here because he wanted to be. Sam was here because he wanted for Dean to be happy, and to share in it.

Castiel felt that same note thrum in his own harmonics. He wanted Dean to be happy, too. Just that. He cared not at all, at that moment, for Michael or Lucifer. If Sam led his brother to what many would call sin, Castiel saw nothing dark in it. Their music was sweeter and brighter for it.

For a time, human months, he went about his work with concern. If the breaking of the seals was part of the Plan, why pretend to fight for them? Zachariah's false gravity at the falling of one seal after another grated on Castiel. Castiel followed orders, but there was no joy in them. The sweet notes of Sam and Dean-now, their life and love always in his awareness, was a selfish comfort as the apocalypse came ever closer.

+++ 

A discord, crashing through, startled Castiel. He sent himself to the hotel room, and hit a wall, shock rippling through him. A being stood before Sam and Dean. The Trickster god.

Castiel tried to speak, but the being stilled him without even pausing as he spoke to Sam and Dean, who stood side by side. The Trickster said to Dean, "See, your life, it's pretty good. There's only one problem. Or maybe it's not a problem. But it is an interesting factoid: Sam here knows who you are." Castiel felt the sudden weight in Dean's chest; his own center went heavy in sympathy. The Trickster glanced at Sam and back to Dean. "He's known all along."

Dean breathed, "Sam?" 

"But he's not going to tell you, is he?" the Trickster said, looking squarely at Sam, who radiated fear and guilt. 

_+No.+_ Castiel said, trying to manifest himself. _+Let them be.+_

_-What is a little Power doing here? Who are you?-_

_+I am Castiel, and that is my hand print on Dean.+_

_-Castiel… Hmm. Castiel… Can't say as I've had the pleasure.-_

_+I am an angel of the Lord.+_

The Trickster smirked, but Castiel did not know if the smirk was for him, or for Sam and Dean. The being said to Dean, "It got a little late for honesty, so he went for happiness instead. Understandable, totally. Forgivable? Who knows?" 

The Trickster kept talking, but Castiel could no longer perceive the sound waves, just the light reflecting and cohering, showing that the mouth was moving. Castiel pushed against the wall that was keeping him from anything more than an awareness of the light, and of Dean's harmonics, where wild notes crashed through. Violence. Betrayal. Over it all, the Trickster communicated to Castiel again, while his mouth moved with other words for Sam and Dean.

_-Isn't that spesh-shul?-_ the god said, and even in this etheric conversation, the voice took on a feminine and insulting tone. _-An angel of the Lord.-_

_+What are you, and why are you here?+_

_-Just teaching the boys a little lesson._ -

Castiel tried again to push through, but the Trickster stopped him with the flick of an eyebrow, and a Trickster god should not have that kind of power over him. All Castiel could do was watch and feel the wild fluctuations of now both Sam and Dean, the utter fear and guilt in Sam, the equally deep anger and betrayal in Dean. Castiel wanted to hear what was said, but the Trickster would not let him. From the looks on their faces he could guess. He could guess. The god offered Dean his memories, and as Sam mouthed _No_ , Dean nodded _Yes_.

And Dean's scream crashed through everything, through every part of Castiel's awareness of Dean. The Trickster god was gone, Castiel's deafness lifted, and he found himself in the room, buffeted by the sounds and the crashing vibrations as Dean-then and Dean-now slammed together, waves interfering to amplify some, destroy others, turning the harmonics of _Dean Winchester_ into an incoherent noise of pain. 

He wanted to touch, to sooth, but another presence stayed his hand. _*Not yet.*_

_+Zachariah.+_

_*What happened here?*_ Zachariah did not seem angry or concerned, only mildly interested. 

_+An entity, the Trickster god, lifted the curse. Dean remembers Hell.+_

_*And he also remembers his little slice of Heaven. And he knows he committed sin with his brother.*_ Zachariah smiled, and Castiel thought of the word smarmy again. Also douche. Zachariah said, _*Good*_. And Zachariah, with the etheric equivalent of a backslap, was gone.

Castiel wanted to ask why it was good, but he knew. Zachariah could only see how this would lead Dean to say yes to Michael. Castiel's distaste for his superior was washed over by the stridency of Dean and Sam's emotions. Dean's pain spiked through, his harmonics clashing. His body was on the floor, tears of memory, of pain, of anger, of loss wracking out of him. Sam wrapped himself around Dean, protecting, bereft. 

Finally Dean stood, and as they argued, each exchange was like a wind on the ocean, pushing up the waves of Dean's harmonic, discordantly, until they were high enough to threaten to destroy Dean's fundamental frequency, the core note of his being.

Castiel whispered to Sam, _+Tell him. Tell him what you tried to do.+_

Sam took a breath. "Just tell me one thing," he said, and Dean stopped, the noise in his harmonic cohering into a tense thrum. Castiel gently prodded, and Sam said, "How is what I did worse than what you did to me? You sold your soul. You went to Hell and I begged a crossroads demon to swap places with you but I couldn't, it wouldn't take the deal." 

Dean turned at that, shock disrupting the waves his anger. 

_+Tell him+_ Castiel whispered again.

"I wanted to be dead and in Hell, Dean. You did that to me. You did it to us. So, yeah, I did a selfish, bad thing because it hurt too much not to do it. I'm not the only one."

The words after didn't matter. The revelation that Sam had tried to take Dean's place in Hell rang through Dean in the purest note of love. But then anger overlaid it, at Sam, at himself. The pain of knowing what he'd done to Sam threaded through it all, but the waves no longer spiked so dangerously.

And when Dean folded to the floor again, Sam wrapping himself around to protect again, the notes still rang discordantly, and Sam was hollow with loss. He did not know, as Castiel could, that one of the foremost griefs within Dean was the loss of his lover, of the life he had loved.

Castiel whispered to Sam. _+Dean still remembers what it feels like to be happy, to desire life and all its small victories. To love you for you. And he does love you, in all ways. If you help him remember that, he will live+_ And to himself he thought, _And he will have no reason to take Michael._

Castiel gave Dean the only gift he could—sleep. 

Sam carried Dean to the bed, and Castiel made sure that Dean did not wake at the movement. Sam curled behind him. 

Castiel kept vigil through the night as Dean slept soundly and Sam woke at every noise. He let Dean wake when Sam went to wake him, and he waited through the harsh words, because they were laden with love, but waiting to see if he needed to whisper again. Then Dean straightened and said, "I need food to do this. Fuck, I need bacon. Like, a pound of bacon and a cinnamon bun the size of Princess Leia's hair."

The sudden joy that shot through Sam's notes showed on his face in a grin. This was Dean-now, hungry for everything. Castiel could feel Sam's thought, that Sam had given Dean enough time for the memories of Hell to fade. Castiel disagreed. The memories of Hell were there, and sharp, but Hell had taken all the light from Dean-then. He had abandoned hope. Sam had given Dean-now a light that Hell had never touched, a love born purely for its own sake. More light, more love, than Dean-then could have ever understood to exist, much less feel worthy enough to accept, or give.

Dean had all the waveforms to make a new whole, and they would settle into a strong harmonic, and there would be no hollow spaces in him. Michael would not find a vessel there.

**Author's Note:**

> With [rivkat](http://archiveofourown.org/users/rivkat/pseuds/rivkat) as my assignment, I was spoiled for choice, but when I read [Only Sweeter](https://archiveofourown.org/works/3188), I wondered where was Castiel. Also, I have a thing for making things weave into canon. How would this situation, rivkat's original story, play out?


End file.
